PROJECT SUMMARY/ABSTRACT The broad objectives of this NRSA Individual Postdoctoral Fellowship are two-fold: 1) to mentor the candidate to become a successful physician-scientist through development of the necessary skills as described in her training plan, and 2) to uncover the mechanisms that direct regulatory T cells to orchestrate resolution of severe lung injury throughout the lifespan. The candidate and her mentors have designed a detailed training plan tailored to the candidate?s specific needs and goals. The proposal focuses on the study of influenza A-induced lung injury, its clinical counterpart the acute respiratory distress syndrome (ARDS) and how they both disproportionately affect the elderly population. Despite decades of dedicated research, there are only a few antiviral drugs available to target the IAV and no specific therapies for ARDS. Regulatory T (Treg) cells have been shown to decrease inflammation and promote tissue repair through the expression of growth factors, such as amphiregulin, in mouse models of lung injury. Treg cells also increase in the lungs of patients with ARDS, suggesting that they may play a role in the human adaptive immune response to lung injury. DNA methylation regulates Treg cell lineage identity and functional reprogramming throughout the lifespan in response to contextual cues. Whether the age- related loss of Treg cell pro-recovery function and increased susceptibility to IAV-induced lung injury in aged hosts is due to changes in their transcriptome or epigenome remains unknown. The focus of this proposal is to understand how age-acquired DNA methylation patterns lead to changes in Treg cell-specific transcriptional and functional programs to drive a dysregulated repair response following influenza A virus infection. The long-term hope of the proposal is to identify novel small molecule- and cell-based therapeutics to control inflammation and promote tissue repair in our increasingly older population. In Specific Aim 1, the candidate will determine whether the failure of aged Treg cells to resolve IAV-induced lung injury results from cell-autonomous or microenvironmentally-driven changes in their transcriptome, epigenome and function. In Specific Aim 2, the candidate will determine whether aging causes loss of Treg cell pro-repair function by decreased expression of amphiregulin. We will use standard techniques to assess severity of lung injury, heterochronic (age mis-matched) adoptive Treg cell transfer, a tamoxifen-based inducible system in mice, flow cytometry, fluorescence-activated cell sorting, transcriptional profiling with RNA-sequencing and DNA methylation profiling with modified reduced representation bisulfite sequencing as the primary methods to support the experimental design of this proposal.